您如何进行将短信发送到一个特定号码的活动

Question

我正在尝试进行消息传递活动，其中，当用户发送短信时，短信会发送到特定的电话号码。此刻，每次单击发送按钮并且没有消息发送时，应用程序都会崩溃。请帮助

这是我的活动java类的代码：

public class Main2Activity extends AppCompatActivity {

    private static final int PERMISSION_REQUEST_CODE = 1;
    private Button sendSMS;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        final EditText phoneNumber = (EditText) findViewById(R.id.editTextarea1);
        if (Build.VERSION.SDK_INT >= 23) {
            if (checkPermission()) {
                Log.e("permission", "Permission already granted.");
            } else {
                requestPermission();
            }
        }

        final EditText smsText = (EditText) findViewById(R.id.message);
        sendSMS = (Button) findViewById(R.id.sendSMS);
        sendSMS.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View view) {
                String sms = smsText.getText().toString();
                String phoneNum = phoneNumber.getText().toString();
                phoneNum="+260893120021";
                if(!TextUtils.isEmpty(sms) && !TextUtils.isEmpty(phoneNum)) {
                    if(checkPermission()) {

//Get the default SmsManager//

                        SmsManager smsManager = SmsManager.getDefault();

//Send the SMS//

                        smsManager.sendTextMessage(phoneNum, null, sms, null, null);
                    }else {
                        Toast.makeText(Main2Activity.this, "Permission denied", Toast.LENGTH_SHORT).show();
                    }
                }
            }
        });
    }

    private boolean checkPermission() {
        int result = ContextCompat.checkSelfPermission(Main2Activity.this, Manifest.permission.SEND_SMS);
        if (result == PackageManager.PERMISSION_GRANTED) {
            return true;
        } else {
            return false;
        }
    }

    private void requestPermission() {
        ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.SEND_SMS}, PERMISSION_REQUEST_CODE);

    }

    @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
        switch (requestCode) {
            case PERMISSION_REQUEST_CODE:
                if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {

                    Toast.makeText(Main2Activity.this,
                            "Permission accepted", Toast.LENGTH_LONG).show();

                } else {
                    Toast.makeText(Main2Activity.this,
                            "Permission denied", Toast.LENGTH_LONG).show();
                    Button sendSMS = (Button) findViewById(R.id.sendSMS);
                    sendSMS.setEnabled(false);

                }
                break;
        }
    }
}